Retinal Implant Restores Some Sight to Blind

Nov. 3, 2010 -- Three blind patients treated with an experimental eye implant were able to see shadows and shapes after getting the device, raising hopes that a highly anticipated new approach to treating blindness may be on the horizon.

Eberhart Zrenner, MD, of Germany’s University of Tubingen Eye Hospital, says close to 30 research groups are working on retinal implants designed to restore sight to the blind; Zrenner’s study is one of only two that have been tried in humans.

The three patients included in the newly published report had gone blind as a result of hereditary retinal degeneration.

Within days of having a tiny microchip surgically implanted, the two men and one woman could see shadows and were able to recognize some shapes.

One man was able to recognize that his fiancée was smiling at him, Zrenner tells WebMD.

How the Implant Works

The microchip, which is just slightly bigger than a sesame seed, includes 1,500 light sensors connected to amplifiers and electrodes. The microchip is designed to sense light and -- with the help of still functioning neurons in the retina -- transmit light signals to the brain.

The implants are controlled by a small handheld external unit, which receives signals from a coin-sized device implanted under the skin directly behind the ear. This device is connected to the chip in the retina, Zrenner says.

The retinal implant allows patients to distinguish between highly contrasting light and dark images. The idea is that the brain can learn to interpret these lines and shapes into meaningful images.

A total of 11 patients received the chip device in the pilot study starting in 2005, but the researchers changed the placement the chip in the retina after the first eight patients were treated in an effort to improve outcomes.

According to the report in the journal Proceedings of the Royal Society B, the last three patients treated were able locate bright objects on a dark table after receiving the implant, and two of the three could name some specific objects the first time they saw them.

One patient could describe objects like forks and knives and different kinds of fruit on the table, as well as correctly identify large, white shapes and letters placed on a black background.

“This was certainly not normal vision,” Zrenner says. “But for people who have been completely blind for years, even this limited improvement can make a difference.”